High-temperature ductile alloys



United States Patent 3,390,984 HIGH-TEMPERATURE DUCTILE ALLOYS Clayton D. Dickinson, Port Washington, and Sam Friedman, Great Neck, N.Y., assignors to General Telephone 3,390,984 Patented July 2, 1968 ice to-brittle transitions for rhenium containing alloys occur in the range from 25 C. to +100 C. in comparison with 175 C. for unalloyed tungsten. The recrystallization temperatures for unalloyed tungsten is between 1450 git} Electronics Laboratories, Inc., a corporation of 5 C. and 1500" C. whereas the present alloys have recrystale aware lization temperatures in the range 1600 C. to 1875 C.

No Drawing- Flle M 1955 443,692 The high strengths and high recrystallization tempera- 6 Claims (CL 75-176) tures obtained in these tungsten-base alloys is believed due to the formation during fabrication of uniformly ABSTRACT OF THE DISCLOSURE 10 dispersed particles of thorium carbide having particle sizes predominantly 1n the range 200 to 1000 Angstroms.

A group of tungsten-base alloys containing 0.03 to 0.4% thorium, 0.002 to 0.03% carbon and up to 7.0% EXAMPLE I rhenium. These alloys exhibit low ductile-to-brittle transition temperatures, high strength at elevated temperatures Elemental powders of thorium, carbon. r m and d hi h t lli i tempi-a[ures tungsten were blended to form a uniform mixture which was then subjected to a pressure of approximately 50,000 pounds per square inch to form a billet. The 'billet was This invention relates to tungsten-base alloys characternext Sintered at a temperature of about 2350 f ized b high strength at l t d temperatures d {Q approximately 4hours to mutually diffuse the different intungsten-base alloys which combine high elevated tempergradients thereby forming a solid solution Of ihOl'llJlTl and ature strength with a low ductile-to-brittle transition teml'h'inium in tungsten, the C bon probably being partit tioned between tungsten carbide and a solid solution of The tungsten-base alloys of the present invention concarbon in tungsten. The billet was then fabricated by tain rhenium, carbon and thorium. As is well known, the forging at a timpefflture of pp ly 1 0 C. from addition of rhenium to tungsten produces alloys having inch to inch thick followed by rolling at a temreduced ductile-to-brittie transition temperatures but the pcrature of about 1550 C. to form sheets having a thickscarcity and high cost of rhenium have limited the use ness of approximately 0.040 inch. During the fabrication of these materials for many applications such as sheet, process, carbon precipitates as finely dispersed thorium tubing and other wrought forms. Accordingly, it is an carbide. While a powder metallurgy process was used in object of the i venti o provide alloys which employ forming the sheets, it shall be understood that the alloys relatively small amounts of rhenium yet have low ductiley also be Consolidated y other Suitablfl Processes 511611 to-brittle transition temperatures, high strength at eles v c um arc-casing. Fabrication may be accomplished vated temperatures and high recrystallization temperay other c niques such as extruding, forging or drawing tures. to produce the desired wrought form.

In he present invention, tungsten-base alloys are pro- Measurements of ultimate tensile strength, recrystallizavided hi h o tain up t 70% heniu 0.002% to tion temperature and ductile-to-brittle transition tempera- 0.03% carbon and between 0.03% to 0.4% thorium. ture were carried out for a number of alloys. The re- (All percentages given are by weight.) In addition, alloys crystallization temperature was established by determinhave been produced which contain only tungsten, carbon ing at what temperature the alloy must be heated for and thorium, these alloys having high elevated temperaone hour "before the fibrous structure completely disture strength although they lack ductility at low temperappears and recrystallization is essentially complete. The atures. By varying the constituents within the specified transition from ductile-to-brit-tle behavor, which occurs ranges the best combination of mechanical properties and over a range of temperatures, was measured by attemptease of fabricability may be obtained for a given applica- 4 ing to bend specimens 1 inch long by /8 inch wide by tion. 0.04 inch thick over a radius four times the thickness of Compared with unalloyed tungsten made by the same the sheet through a 105 angle at several temperatures process the present alloys are generally stronger at 1650" and determining the minimum temperature at which the C., have higher recrsytallization temperatures and, when sample cracked after a small but perceptible amount of rhenium is incorporated, are ductile at lower temperatur s. bending (nil ductility temperature) and the minimum In particular, a number of the alloys in the system are temperature at which the sample bent 105 without crackcompletely ductile at room temperature or below. For ing (ductility temperature). example, the alloys exhibit ultimate tensile strength at Characteristics of the alloys at different compositions 1650 C. in the range 23,000 p.s.i. to 43,000 p.s.i. as comare shown in Table I. A dash in the table indicates that pared to 13,000 p.s.i. for unalloyed tungsten. The ductilethe listed property was not measured for that sample.

TABLE I Alloys, Percent Ultimate Ductile-to-Brittle One Hour by Weight Tensile Transition Temp. C.) Recrystalli- Strength zation Temp. Th Re C W at 1,650 C. Nil Det. Ductility C.)

' (p.s.i.) Temp. Temp.

0. 0s 5. 0 0. 012 Balance 32, 000 05 1, 700-1, 750 0.10 5.0 0. 010 Balance 50 -25 0. 15 1. 0 0. 010 Balance 41, 000 10 25 1, 800-1, 825 0. 15 3. 0 0. 009 Balance 39, 000 25 100 1, 725-1, 750 0. 15 7. 0 0. 004 Balance 23, 000 10 1, 600-1, 025 0. 35 5. 0 0. 003 Balance 35, 000 25 10 1, 650-1, 675

0 EXAMPLE II An alloy consisting of thorium. carbon and tungsten was prepared by the method described for the ailov of Example I. Table 11 gives the characteristics or various compositions of this alloy.

thorium. 0.01% carbon and 1.0% rhenium, the balance tuztinsisting of tungsten.

tl. A tungsten-base alloy characterized by high strength at elevated temperatures consisting essentially of 0.03% to 0.13% thorium and 0.004% to 0.3% carbon, the balance consisting of tungsten.

From these results it is apparent that those alloys containing at least 1% rhenium exhibit high Strength at elevated temperatures and are ductile at low temperatures. Thorium-carbon-tungsten alloys Without rhenium have high elevated temperature strength but are not ductile at low temperatures. All of the disclosed alloys have high recrystallization temperatures as compared to unalloyed tungsten. For applications where a high melting point is desired, the composition containing the minimum alloying ingredients consistent with desired mechanical properties have been found most suitable.

As many changes could be made in the above described compositions it is intended that all matter contained therein shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An alloy consisting essentially of 0.03% thorium, 0.003% to 0.03% carbon, and up rhenium, the balance consisting of tungsten.

2. An alloy consisting essentially of 0.08% thorium, 0.003% to 0.19% carbon. and 1.0% rhenium, the balance consisting of tungsten.

3. A tungsten-base alloy characterized by high strength at elevated temperatures and a low ductile-to-brittle transition temperature consisting essentially of about 0.15%

.15. A tungsten-base alloy characterized by high strength at elevated temperatures and low ductile-to-brittle tranttition temperature consisting essentially of from 0.10% to 015% thorium, 1% to 7% rheniuni, and 0.004% to 0.019% carbon, the balance consisting of tungsten.

16. An alloy consisting essentially of 0.03% to 0.04% thorium. 0.003% to 0.03% carbon and up to 7% rhenium, the balance consisting of tungsten, said alloy containing uniformly dispersed particles of thorium carbide having particle sizes predominantly in the range E00 to 2000 angstroms.

References Cited UNITED STATES PATENTS 30.580.171 112/1951 Hagglund et al. 75-124 3,116.145 i2/1963 Semchyshen 75176 3.236.699 13/1966 Pugh et al. 75-176 3,243,291 M1966 Dickinson et a1. 75l76 lIIDTHER REFERENCES Nb. Ta. Mo and W, Quarrell, Elsevier Publishing Co., Il' lew rorlt. 1961. relied on pp. 321 and 347-361.

tIIIHARLES N. LOVELL, Primary Examiner. 

